COMP: Add global option allowing to skip install of CLI shared library

Option is named "SlicerExecutionModel_NO_INSTALL_CLI_SHARED_LIBRARIES", if
not already set, its value will default to "FALSE".

If set to False, it means that CLI shared library will be installed. This
reveals to be particularly useful when generating MacOSX bundle where
library are automatically copied using the fixup mechanism.

See http://www.na-mic.org/Bug/view.php?id=3051
Add option allowing to specify which link flags to use with CLI executable

The SlicerExecutionModle can be configured with option SlicerExecutionModel_DEFAULT_CLI_EXECUTABLE_LINK_FLAGS
or the set of flags to use can locally be overridden setting variable
SlicerExecutionModel_CLI_EXECUTABLE_LINK_FLAGS.
Merge branches 'add-option-to-skip-cli-shared-libs-install' and 'macosx-link-executable-with-rpath' into pu

* add-option-to-skip-cli-shared-libs-install:
  COMP: Add global option allowing to skip install of CLI shared library

* macosx-link-executable-with-rpath:
  Add option allowing to specify which link flags to use with CLI executable